Integrated drive generator housing

ABSTRACT

A method of assembling an integrated drive generator includes the steps of providing a bore in a center housing portion, pressing a bearing liner into the bore, with a portion of the bearing liner extending proud of a surface of the center plate, and machining the surface around and adjacent to the bearing liner to provide a machined surface parallel to the surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This disclosure is a continuation of U.S. patent application Ser. No.13/542,776 filed Jul. 6, 2012.

BACKGROUND

This disclosure relates to a housing for an integrated drive generatorfor a gas turbine engine, for example. The disclosure also relates to amounting configuration for a hydraulic unit of the integrated drivegenerator relative to its housing.

One example type of integrated drive generator (IDG) includes agenerator, a hydraulic unit and a differential assembly arranged in acommon housing. The differential assembly is operatively coupled to agas turbine engine via an input shaft. The rotational speed of the inputshaft varies during the operation of the gas turbine engine. Thehydraulic unit cooperates with the differential assembly to provide aconstant speed to the generator throughout engine operation.

In one example, the housing includes generator, center and input housingportions, which may be constructed from a magnesium alloy. The hydraulicunit is mounted to the center housing portion, which is sealed relativeto the generator and input housing portions with seal plates.

The center housing has spaced apart lateral sides. The hydraulic unitincludes a structural can that is mounted to one of the sides. It can bedifficult to maintain the flatness in a machined magnesium surface. Thesides have been machined flat in the area of the hydraulic unit acrossthe center housing portion in the area of the hydraulic unit and thesurrounding surface, which maintains flatness of the center housingportion to ensure that it adequately seals relative to the other housingportions. A bearing liner is pressed into a bore in the center housingportion to support a hydraulic unit shaft. The bearing liner is flushwith the lateral surface opposite the can. The surface is subsequentlymachined right over the bearing liner, better ensuring flatness.

SUMMARY

In one exemplary embodiment, a method of assembling an integrated drivegenerator includes the steps of providing a bore in a center housingportion, pressing a bearing liner into the bore, with a portion of thebearing liner extending proud of a surface of the center plate, andmachining the surface around and adjacent to the bearing liner toprovide a machined surface parallel to the surface.

In a further embodiment of the above, the method includes the step ofinstalling a bearing onto a shaft, and inserting the bearing into thebearing liner.

In a further embodiment of any of the above, the method includesmachining a recess in an opposite side of the center housing portion toprovide a second machined surface, and securing a hydraulic unit to thesecond machined surface, the hydraulic unit having the shaft.

In a further embodiment of any of the above, the method includesarranging a seal on the machined surface and sealing the center housingportion relative to another housing portion with the seal plate. In afurther embodiment of any of the above, the method includes the steps ofsecuring generator, center and input housing portions to one another.The center housing portion is sealed relative to the generator and inputhousing portions with seal plates. The center housing portion isarranged between the generator and input housing portions. The sealplates are arranged on opposing sides of and in engagement with thecenter housing portion. A hydraulic unit is mounted to the centerhousing portion. The center housing portion includes first and secondparallel surfaces, and the machined surface is parallel to and recessedinto one of the first and second surfaces in an area of the hydraulicunit.

In a further embodiment of any of the above, the method includes thesteps of securing generator, center and input housing portions to oneanother. The center housing portion is sealed relative to the generatorand input housing portions with seal plates. A hydraulic unit is mountedto the center housing portion. The center housing portion includes firstand second parallel surfaces. The machined surface is parallel to andrecessed into one of the first and second surfaces in an area of thehydraulic unit. The hydraulic unit includes a can having a flangesecured to the machined surface. The can houses a shaft supported by abore in the center housing portion.

In a further embodiment of any of the above, the can houses first andsecond pumping elements separated by a pump plate and configured toprovide a fixed rotational speed to a generator within the housing.

In a further embodiment of any of the above, a first lateral thicknessis provided between the first surface and the machined surface. A secondlateral thickness is provided between the first and second surfaces. Aratio of the second lateral thickness to the first lateral thickness is1.05.

In a further embodiment of any of the above, the hydraulic unit includesa shaft supported by a bearing in the center housing portion. Themachined surface surrounds the bearing.

In a further embodiment of any of the above, the method includes thesteps of securing generator, center and input housing portions to oneanother. The center housing portion is sealed relative to the generatorand input housing portions with seal plates. A hydraulic unit is mountedto the center housing portion. The center housing portion includes firstand second parallel surfaces. The machined surface is parallel to andrecessed into one of the first and second surfaces in an area of thehydraulic unit. The hydraulic unit includes a shaft supported by abearing in the center housing portion. The machined surface surroundsthe bearing. The bearing includes a bearing liner extending proud of themachined surface.

In a further embodiment of any of the above, the bearing liner is in aninterference fit in a bore in the center housing portion.

In a further embodiment of any of the above, the bearing liner includesfirst and second flanges opposite one another. The second flange engagesthe second surface. The first flange is proud of the first surface andengages the bearing.

In a further embodiment of any of the above, the bearing is a rollerbearing.

In a further embodiment of any of the above, the machined surface mayprovide a lip circumscribing the bearing liner.

In a further embodiment of any of the above, the center housing portionis a magnesium alloy.

In a further embodiment of any of the above, the machined surface isprovided by a milled surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be further understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings wherein:

FIG. 1 is a highly schematic view of a generator system.

FIG. 2 is a cross-sectional schematic view of an example integrateddrive generator.

FIG. 3 is a schematic perspective view of a generator, a hydraulic unitand a differential assembly of the integrated drive generator shown inFIG. 2.

FIG. 4 is a cross-sectional view through the hydraulic unit.

FIG. 5 is an enlarged cross-sectional view of in an area of a bearingsupporting a hydraulic unit shaft relative to a center housing portion.

FIG. 6 is an enlarged cross-sectional view of the hydraulic unit mountedto the center housing portion.

DETAILED DESCRIPTION

An example generator system 10 is schematically illustrated in FIG. 1.The system 10 includes a gas turbine engine 12 that provides rotationaldrive to an integrated drive generator (IDG) 16 through an accessorydrive gearbox 14 mounted on the gas turbine engine 12. The accessorydrive gearbox 14 is coupled to a spool of the engine 12, and the speedof the spool varies throughout engine operation.

Referring to FIGS. 2 and 3, an example IDG 16 is illustrated. In theexample, the IDG 16 includes a housing 18 having generator, center andinput housing portions 20, 22, 24 secured to one another. A generator 40is arranged in the generator housing portion 20. Seal plates 23 areprovided on either side of the center housing 22 to seal the centerhousing 22 relative to the generator and input housing portions 20, 24.

An input shaft 26 receives rotational drive from the accessory drivegearbox 14. The rotational speed of the input shaft 26 varies dependingupon the operation of the engine 12. To this end, as a result, ahydraulic unit 32 cooperates with the differential assembly 28 toconvert the variable rotational speed from the input shaft 26 to providea fixed rotational output speed to the generator 40.

The input shaft 26 rotationally drives a differential input gear 30 thatis coupled to a hydraulic input gear 34 of the hydraulic unit 32. Thedifferential input gear 30 is operatively coupled to the input shaft 26by the disconnect assembly 27. The hydraulic output gear 36 is coupledto a differential speed trim gear 38. The hydraulic unit 32 increases ordecreases the rotational speed provided to the differential unit 28 fromthe hydraulic input gear 34 to provide a fixed rotational output speed,such as a 12,000 rpm speed. The variable rotational speed of thedifferential input gear 30 combines with the speed of the differentialspeed trim gear 38 to provide a fixed rotational speed to a gear inputshaft 42.

In the example, a gear train 44 cooperates with the generator inputshaft 42, which rotates at a constant speed to rotationally drive acharge pump 46, deaerator 48, main scavenge pump 50, inversion pump 52and generator scavenge pump 54. Thus, these components may be designedefficiently to operate at a fixed speed.

Referring to FIG. 4, the hydraulic unit 32 includes a can 60 that housesand provides structural support for the hydraulic unit components. Fixedand variable speed shafts 62, 64 are arranged coaxially with and nestedrelative to one another on one side of the hydraulic unit 32. Thehydraulic input gear 34 is provided by the variable speed shaft 64, andthe hydraulic output gear 36 is provided by the trim speed shaft 62.

A speed change shaft 72 is also arranged within the can 60 and iscoaxial with the trim and variable speed shafts 62, 64. A pump plate 66separates first and second pumping assemblies 68, 70, which each includea wobbler and pistons. The pumping assemblies cooperate with one anotherto increase or decrease the rotational speed of the trim speed shaft 62.

A first bearing 74 supports the trim speed shaft 62 relative to the can60, and a second bearing 76 supports the other end of the trim speedshaft 62 relative to the pump plate 66. Another second bearing 76supports the speed change shaft 72 relative to the pump plate 66, and athird bearing 78 supports the other end of the speed change shaft 72relative to the center housing 22. A fourth bearing 79 supports thevariable speed shaft 64 relative to the input housing 24.

Referring to FIGS. 4 and 5, the center housing portion 22 includes abore 80 that receives the third bearing 78. A bearing liner 82, whichmay be steel, is press-fit into the bore 80. The bearing liner 82includes first and second flanges 84, 86 adjoined by a wall 88 that isreceived in the bore 80 to provide the press-fit. It is desirable topress-fit the bearing liner 82 into the bore 80 prior to machining,since press-fitting may distort the magnesium center housing portion 22.The center housing portion 22 includes first and second surfaces 98, 100that are laterally spaced apart from one another. The first and secondsurfaces 98, 100 may be provided by an initial machining operation thatmay provide sufficiently flat surfaces for adequate sealing of the sealplates 23. The second flange 86 abuts the second surface 100 to limitthe installation depth of the bearing liner 82 during press-fitting.

The first flange 84 extends proud or beyond the first surface 98, whichis necessary to accommodate the width of the third bearing 78. The thirdbearing 78 includes an outer race 90 received by the bearing liner 82 inabutting relationship with the first flange 84. Rollers 92 are spacedcircumferentially about an inner race 96, which is provided by the speedchange shaft 72, and engage the outer and inner races 90, 96. Thecircumferential spacing of rollers 92 are maintained by a cage 94.

The center housing portion 22 is machined to a thinner width thanprovided by the first and second surfaces 98, 100. This may enable alonger hydraulic unit to be accommodated in the same sized housingenvelope as previously used IDGs. However, desired flatness of thecenter housing portion 22 must be maintained to ensure proper sealing ofthe center housing portion 22 relative to the generator and inputhousing portions 20, 24. To this end, the first surface 98 is machined,for example, using a milling operation, to provide a machined surface102 that is parallel with the second surface 100. The bearing liner 82is installed before machining.

The can 60 includes a flange 106 that is secured to the center housingportion 22. The flange 106 includes holes 108 aligned with holes 110 inthe center housing portion 22. Fasteners 112 are received by the holes108, 110 and secure the flange 106 to the center housing portion 22. Amachined surface 114, provided for example using a milling operation, isrecessed into the second surface 100 to accommodate the longer hydraulicunit and provide a first lateral thickness T1. The first lateralthickness T1 is provided between the first surface 98 and the machinedsurface 114, which are parallel to one another. A second lateralthickness T2 is provided between the first and second surfaces 98, 100.The ratio of the second lateral thickness T2 to the first lateralthickness T1 is 1.05.

Although an example embodiment has been disclosed, a worker of ordinaryskill in this art would recognize that certain modifications would comewithin the scope of the claims. For that reason, the following claimsshould be studied to determine their true scope and content.

1. A method of assembling an integrated drive generator, comprising thesteps of: providing a bore in a center housing portion; pressing abearing liner into the bore, with a portion of the bearing linerextending proud of a surface of the center plate; and machining thesurface around and adjacent to the bearing liner to provide a machinedsurface parallel to the surface.
 2. The method according to claim 1,comprising the step of installing a bearing onto a shaft, and insertingthe bearing into the bearing liner.
 3. The method according to claim 2,comprising machining a recess in an opposite side of the center housingportion to provide a second machined surface, and securing a hydraulicunit to the second machined surface, the hydraulic unit having theshaft.
 4. The method according to claim 3, arranging a seal on themachined surface and sealing the center housing portion relative toanother housing portion with the seal plate.
 5. The method according toclaim 1, comprising the steps of: securing generator, center and inputhousing portions to one another, the center housing portion sealedrelative to the generator and input housing portions with seal plates,wherein the center housing portion is arranged between the generator andinput housing portions, and the seal plates are arranged on opposingsides of and in engagement with the center housing portion; mounting ahydraulic unit to the center housing portion; and wherein the centerhousing portion includes first and second parallel surfaces, and themachined surface is parallel to and recessed into one of the first andsecond surfaces in an area of the hydraulic unit.
 6. The methodaccording to claim 1, comprising the steps of: securing generator,center and input housing portions to one another, the center housingportion sealed relative to the generator and input housing portions withseal plates; mounting a hydraulic unit to the center housing portion;and wherein the center housing portion includes first and secondparallel surfaces, and the machined surface is parallel to and recessedinto one of the first and second surfaces in an area of the hydraulicunit, wherein the hydraulic unit includes a can having a flange securedto the machined surface, the can housing a shaft supported by a bore inthe center housing portion.
 7. The method according to claim 6, whereinthe can houses first and second pumping elements separated by a pumpplate and configured to provide a fixed rotational speed to a generatorwithin the housing.
 8. The method according to claim 7, wherein a firstlateral thickness is provided between the first surface and the machinedsurface, a second lateral thickness is provided between the first andsecond surfaces, and a ratio of the second lateral thickness to thefirst lateral thickness is 1.05.
 9. The method according to claim 5,wherein the hydraulic unit includes a shaft supported by a bearing inthe center housing portion, the machined surface surrounding thebearing.
 10. The method according to claim 1, comprising the steps of:securing generator, center and input housing portions to one another,the center housing portion sealed relative to the generator and inputhousing portions with seal plates; mounting a hydraulic unit to thecenter housing portion; and wherein the center housing portion includesfirst and second parallel surfaces, and the machined surface is parallelto and recessed into one of the first and second surfaces in an area ofthe hydraulic unit, wherein the hydraulic unit includes a shaftsupported by a bearing in the center housing portion, the machinedsurface surrounding the bearing, wherein the bearing includes a bearingliner extending proud of the machined surface.
 11. The method accordingto claim 10, wherein the bearing liner is in an interference fit in abore in the center housing portion.
 12. The method according to claim11, wherein the bearing liner includes first and second flanges oppositeone another, the second flange engaging the second surface, and thefirst flange proud of the first surface and engaging the bearing. 13.The method according to claim 12, wherein the bearing is a rollerbearing.
 14. The method according to claim 10, wherein the machinedsurface may provide a lip circumscribing the bearing liner.
 15. Themethod according to claim 5, wherein the center housing portion is amagnesium alloy.
 16. The method according to claim 15, wherein themachined surface is provided by a milled surface.